The Solana Privacy Hack brought together builders exploring how to implement confidential transactions responsibly on a high-performance blockchain. With more than $140,000 in prizes across 17 bounties, the hackathon attracted teams focused on private payments, zero-knowledge infrastructure, and privacy-preserving developer tools.

Range sponsored a bounty focused on compliant privacy: privacy infrastructure that integrates screening, selective disclosure, or onchain risk verification. The goal was simple. Demonstrate how privacy-preserving systems can operate while still enforcing safeguards against sanctioned or high-risk actors.

After reviewing submissions, three projects stood out for their technical execution and alignment with that goal:

1. Turbine Cash

2. Mixoor

3. Settlr Pay

Each project explored a different layer of the privacy stack - from compliance infrastructure to private payments and merchant settlement. Below is a closer look at what these teams built and why their ideas matter for the future of privacy on Solana.

Turbine Cash: Enabling onchain wallet screening

Range Onchain Verification Support Program was developed by the team behind Turbine Cash, a live privacy protocol on Solana.

Turbine Cash provides privacy-preserving token transfers using cryptographic techniques that break the onchain link between a sender and recipient. Similar to other privacy pools, users deposit funds into a contract and later withdraw them to a different wallet without revealing which deposit funded the withdrawal.

The hackathon project focused on making Range wallet risk screening easily enforceable directly onchain.

The team built a framework that allows privacy protocols to integrate Range's risk signals within their program logic. This enables smart contracts to verify wallet risk status before allowing users to interact with the protocol.

Key capabilities include:

• Onchain risk verification: Wallets interacting with the protocol can be checked against Range risk signals.

• Pre-deposit compliance checks: Deposits can be blocked if an address is flagged by risk screening.

• Reusable integration module: The framework makes it easier for other privacy protocols to adopt the same compliance architecture.

This approach strengthens the compliant privacy model. Privacy pools can preserve anonymity for legitimate users while preventing deposits from wallets associated with sanctions lists, hacks, or illicit activity.

By simplifying how developers integrate these checks, the Turbine Cash team demonstrated a practical path toward compliance-aware privacy infrastructure across Solana.

Mixoor: Privacy-preserving transfers with built-in compliance

Mixoor is a privacy protocol that enables unlinkable transfers of SOL, USDC, and other SPL tokens on Solana.

The system uses zero-knowledge proofs (zk-SNARKs) to break the onchain link between deposits and withdrawals. This allows users to transact privately without exposing their full financial history.

The protocol operates through a two-phase flow.

First, during the deposit phase, users deposit tokens into a privacy pool. A cryptographic commitment is generated client-side using a combination of a secret value, a nullifier, the transfer amount, and the pool identifier. This commitment is added to a Merkle tree that tracks all deposits.

Second, during the withdrawal phase, the user generates a zk-SNARK proof demonstrating that they control a valid commitment in the pool - without revealing which one. A relayer then submits the withdrawal transaction, sending funds to the recipient address.

This design ensures there is no onchain link between the original deposit and the withdrawal transaction.

Mixer now also supports direct transfer flows with multiple recipient wallets.

What made Mixoor stand out in the Range bounty was its integration of compliance screening directly into the deposit flow.

Before funds enter the privacy pool, the protocol performs:

• Wallet risk screening using Range's Risk API

• Validation checks to ensure addresses are not flagged

• Compliance-aware deposits while preserving user privacy

If an address is associated with known illicit activity, the deposit can be blocked before funds enter the pool.

This architecture demonstrates how zero-knowledge privacy systems can operate alongside compliance safeguards, making them more viable for real-world adoption.

Settlr Pay: Private, gasless USDC payments for merchants

Settlr Pay takes a different approach to privacy infrastructure by focusing on merchant payments and global payouts.

Settlr is building a payout platform that allows companies to send money worldwide using only an email address. Instead of requiring bank details, routing numbers, or SWIFT codes, platforms can send payouts through a simple API call.

The workflow is straightforward:

1. A platform sends a payout request containing an email address and amount.

2. The recipient receives a secure claim link.

3. The recipient claims the payout to any Solana wallet.

4. Future payouts can be delivered instantly since the platform remembers the recipient's wallet.

Payments settle instantly onchain in USDC, with support for recipients in more than 180 countries.

The team's hackathon project focused on adding privacy and usability improvements for onchain payments, including:

• Shielded transaction flows

• Gasless payment experiences

• Simplified onboarding for recipients unfamiliar with crypto

For businesses distributing funds globally - such as marketplaces, payroll systems, and creator platforms - this model removes many of the operational barriers that exist in traditional payout systems.

Settlr charges a 1% flat fee per payout while delivering near-instant settlement on Solana.

Building privacy infrastructure that can scale

The projects submitted to Range's bounty demonstrated a clear trend: privacy infrastructure on Solana is evolving toward compliance-aware architectures. Instead of treating privacy and compliance as opposing forces, these teams built systems that allow both to coexist.

Across the three winning projects - Turbine Cash, Mixoor, and Settlr Pay - we saw several key patterns:

• Onchain risk verification integrated into privacy protocols

• Zero-knowledge privacy with pre-deposit compliance checks

• Privacy-preserving payment flows for real-world financial use cases

This approach aligns with the broader direction of privacy development across the ecosystem. As confidential infrastructure matures, protocols need tools to maintain privacy while meeting regulatory and operational expectations.

Our Risk API and Onchain Risk Verifier provide the compliance layer that enables this model. Builders can screen wallets before deposits, enforce risk rules directly in smart contracts, and maintain selective disclosure when compliance verification is required.

Range will continue supporting teams building privacy systems that integrate risk screening, compliance verification, and observability from day one.

If you are developing privacy infrastructure on Solana and want to integrate our Risk API and Onchain Risk Verifier, explore our documentation or get in touch with our team.

Privacy is becoming a core feature of blockchain infrastructure. Building it responsibly ensures that it can scale across ecosystems and institutions alike.